Surgical treatment of fractured bones, osteoporotic bones, deformed bones and the like usually requires gaining an access into the interior of the bone as a first stage. When minimally invasive surgery is involved, such as percutaneous surgery, the step of accessing the bone is limited by dimensional requirements. The preferred tool should have minimal diameter and should provide safe and minimally invasive access into the bone in an uncomplicated manner.
Fixation of vertebral body fractures, for instance, may comprise fracture reduction and/or creation of a void in the cancellous bone, followed by injection of bone void filler/bone cement (PMMA), in order to reinforce the vertebral body. Exemplary fixation of this type is described in PCT/IL2004/000527; and U.S. Pat. Nos. 4,969,888 and 5,108,404 which are each fully incorporated herein by reference. The standard procedure includes gaining an access into the vertebral body optionally through the pedicle, using a needle and stylet assembly (such as Jamshidi needle), having a diameter of about 2.5-3.5 mm. The inner stylet is removed and replaced with a guide wire of about 1.5 mm diameter. Then, a small incision is made in the skin, and a trocar with a cone-shaped distal end is introduced over the guide wire, to enable passage through soft tissue. A cannula of about 4-6 mm diameter is introduced over the trocar, up to the pedicle, and the trocar is removed. Optionally, the trocar and cannula are assembled and introduced together. At this stage, a cannulated 3-6 mm diameter drill/reamer is advanced over the guide wire and via the cannula to enlarge the passage into the vertebral body. Optionally, the trocar and the drill are combined to one reamer. Normally, a manually operated drill/reamer is used. The guide wire and drill/reamer are removed, leaving the cannula inside the body. The rest of the procedure may proceed through the cannula. As can be seen, accessing the bone is a multiple-stage procedure, which is time consuming.
Lately a more shortened procedure is being used, during which a larger diameter Jamshidi needle is firstly introduced into the vertebral body. Following insertion, the stylet is withdrawn and the drilling stage and the rest of operation proceed via the needle, which serves as a working sleeve. Typically, positioning the Jamshidi needle into the pedicle may require several insertions (e.g., trial and error attempts) into the pedicle.